490 



Prof. C. S. Sherrington. 



[Jan. 31, 



shown conversely that similar stimulation of the afferent fibres of the 

 extensor muscle (vasto-crureus) inhibits contraction of the flexor muscle. 

 To examine this latter point is not altogether easy, since the nerve severance 

 of the vasto-crureus nerve, in order to stimulate its central end, of necessity 

 renders impossible the maintenance, let alone the examination, of any 

 reflex status of that muscle. I have, however, succeeded in splitting the 

 nerve, and if that is done without too much damage to either half of it, 

 one division can be severed and dissected back into the psoas, and the 

 other remain preserving the knee-jerk and, more important, a fair extensor 

 tonus at the knee. The central end of the severed division can then be 

 stimulated, and its effect on the rest of the extensor muscle itself be thus 

 observed. 



To employ electrical stimulation with as little risk of escape of current 

 as possible it is necessary to cut the divided nerve as low as possible, and 

 dissect it up into psoas as high as possible ; in this way I have obtained 

 sometimes 5 cm. length of free nerve. I have further exsected the internal 

 saphenous nerve right up into the psoas, and also the external division of 

 the muscular division of the anterior crural nerve, hoping thus to minimise 

 current escape from the stimulated branch of vasto-crureus nerve to those 

 other branches of the anterior crural. In a previous communication I 

 discarded effects of electrical stimulation of the nerve of the extensor 

 muscle as too open to error by escape of current.* Further examination 

 with the above precautions makes me, however, regard the following as 

 reliable reflex effects obtainable by stimulation of the central end of the 

 vasto-crureus nerve itself : inhibition of the tonus of vasto-crureus itself, 

 the tonus returning to some extent immediately on cessation of the stimulus 

 if the stimulus be weak and brief ; inhibition of the knee-jerk, contraction 

 of rectus femoris, especially of its upper part, and tensor vaginas femoris 

 and psoas, dorso-flexion of ankle, some slight contraction of the hamstring 

 muscles, especially deep inner hamstring, and extension of opposite knee with 

 inhibition of its hamstring muscles. These effects obtained by faradic 

 excitation are also obtainable, but in slighter measure, by drawing a ligature 

 tight upon the central end of the nerve (mechanical stimulation). The 

 total effect is flexion of the homonymous and extension of the opposite limb. 



There is thus no evidence that the afferent nerve-fibres from this extensor 

 muscle when excited in these ways inhibit contraction of the flexors, 

 although the afferent fibres from the knee-flexor when similarly excited do 

 inhibit contraction of this extensor. Eeciproeal innervation is evident in 

 the reflex effect obtained from the afferents of each muscle, for those of 

 * ' Boy. Soe. Proc.,' B, vol. 16, p. 283. 



